Internal-combustion engine



June 17, 1930. D. P. SAVAGE 1,764,530,

INTERNAL COMBUSTION ENGINE Filed April 15, 1929 is O INVENTOR.

:a BY -1 W A TTORNE YS.

Patented June 17, 1930 PATENT "oFFicE DAVID PRAINGLE sAvAeEQoF SYDNEY, NEW sourn -WALES, AUSTRALIA INTERNAL-COMBUSTION ENGINE Application filed A ril 15,

o a My invention relates to internal combustion engines and more particularly to the pistons thereof.

The principal object of the invention is to provide greater piston displacement on the expansion or power stroke than on the suction or intake stroke, thereby increasing thethermal efliciency of the engine by lowering the temperature of the burned gases at the end of the power stroke, and simplifying the problem of cooling the cylinder, piston, and valves, especially in high-compression engines and engines of the Diesel type. A second object of the invention is to provide a more rapid rate of expansion, so

that the beneficial eifects of the lower temperature of the burned gases begin immediately after firing the charge. Other objects and advantages will become apparent from the following specification, which should be read with the understanding that the form, arrangement and construction of the several parts may be varied, within the limits of the claims hereto appended, without departing from the spirit of the invention as set forth therein. I achieve the above objects by providing a two-part piston, comprising an outer open ended sleeve member sliding within the cylinder and a core member of materially smaller diameter *slidably fitted within said sleeve. One of said members, preferably the core, is connected with the crank shaft by the usual connecting rod. During the intake and compression strokes, (in a four-cycle en: gine) the sleeve is held stationary, so that the displacement is only that of the core, but upon the expansion and exhaust strokes both members move together, so that the displacement is that of the entire piston.

I am aware that" pistons have been providedin the past with sliding connections be tween the piston head and the crank pin,

' whereby the stroke of the piston head is reduced upon the intake and compression strokes and increased upon the expansion and exhaust strokes,the piston head traveling only through the initial portion of the stroke during the intake, then remaining stationary until the final portion of the com- 1929. Serial no, 35,5,o94.

pression stroke, and traveling'the full-stroke during expansion and exhaust. Insuclrconstructionthe increased piston displacement is secured by increasing the time rather than the rateof -expansion, so that no coolmg effeet is produced at the beginning of the ex- 7 panision stroke when it is most needed.-

My invention will now be described fully with reference to the accompanying drawings, wherein Fig.1is a longitudinal section of an engine cylinder provided with my improved piston, showingone means for preventing hammering of the sleeve member.

Fig. 2 is a transverse section on the line 2-2 of Fig; 1'. a

Fig. 3 is a longitudinal section showing a second means for preventing hammering of the sleeve.

In the drawings, the reference numeral 1 designates an engine cylinder having the usual valves 2. The crank-case, crank-shaft,

connecting rod, and'other parts of theengine The core 5, therefore, travels in the usual.

manner for the full stroke throughout the cycle. Its diameter, asshown, is materially less than that of the cylinderl.

The sleeve 4 has aninwardly.projecting flange 8 at itsupper. end, adapted'to engage a shoulder-9 near theupperend of the, core 5. The sleeve therefore cannot movebelow the core atany time, but the core is free to move downwardly within the sleeve.

p A suitable locking mechanism is provided for holding the sleeve Jr-stationary atthe upper limit of its travel during the suction and compression strokes of the core 5, and for freeing said sleeve to permit it to travel with the core during the expansion and exhaust strokes. I prefer to employ a' cam operated latch, two essentially similar forms of which are shown respectively in Figs. 1 and 3. In both forms a cam 10 is carried by a shaft 11, which maybe the usual cam shaft of the engine, and which rotates at half the speed of the crank shaft. In Fig. 1 the cam operates a lever 12 whose lower end is formed with a latch 13 adapted to engage a flange 14 extending outwardly from the lower end of the sleeve 4. In Fig. 3 the cam operates a rod 12 connected with a latch member 13 adapted to engage the lower end of the sleeve 4:. The cam 10 is so timed that the latch, (1301' 13) engages the sleeve at the end of the exhaust stroke, and holds it until the be inning of the expansion stroke.

In order to prevent hammering of'the sleeve 4 at the upper end of its travel, I provide a buffer ,mechanism which maybe either a spring device as in Fig. 1, or a pneumatic cushion as in Fig. 8. In Fig. 1 there are a number of guide rods 15 secured to and extending downwardly from the cylinder 1. The flange 14 of thesleeve t has holes enabling it to slide freely upon said rods. Springs 16 surround the. upper portions of said rods and are preferably secured to. the cylinder, as by welding inclicated at 17. The springs are of such. a length as to be considerably, compressed by the flange 14 when the sleeve 4 reaches the :upper end of its stroke, thus acting as a cushion to prevent said sleeve from hammering against the cylinder. Resilient washers-18, of leather, or other suit-able .material, may be mounted upon the flange 14 to prevent metallic clicking when said flange strikes the springs 16. V

In Fig. 3 an air cushionis provided by enlarging the diameter of the lower ends of the cylinder 1 and the sleeve 4;, forming shoulders 19 between which air is trapped and compressed when said sleeve approaches the upper end of its travel. One or more vent passages 20, provided with check valves 21,. connect the compression space between said shoulders with the atmosphere, so that air is freely admitted upon the down stroke of the sleeve, but is trapped and compressed upon the'up 'strokeQ I The operation of my piston willbe apparent from the foregoing description. It is shown in Fig. 1 at the beginning of the suction stroke. The latch 13 has just engaged the flange 14, and will so remain, holding the sleeve l stationary, during the en suing suction and compression strokes of the core 5. ig. 3, the latch is about to release the sl eeve 4, which occurs at the beginning of the expansion stroke. The sleeve and the core then travel together through the expansion and exhaust strokes, thus completing the cycle.

, When the engine is operating, the pressure within the cylinder is always sufficient during the expansion and exhaust strokes, when the sleeve 4 is free to move with the core 5, to keep the flanges 8 and 9 of said sleeve and piston in firm contact, preventing hammering or rattling. In starting, or shutting down the engine, however, when the cylinder charge is not fired, the cylinder pressure may drop below atmospheric during the expansion and exhaust strokes. To prevent hammering between the sleeve 4 and core 5 under such conditions, I rovide means forkeefping the sleeve stationary throughout the entire cycle. This may best be accomplished by making the cam 10 slidable upon its shaft 11, as indicated by the key ways 22. The cam may then be moved axially, when starting and stopping the engine, to free it from the latch operating member (12 or 12). and to cause the latch to engage and hold the sleeve. continuously.

I claim 1. In an engine, a cylinder; a piston comprising an open ended sleeve member and a core member, one of said members being connected with the engine crank shaft and the other member moving therewith for a portion of the cycle; means controlled 'by said shaft-connected member for holding said other member stationary for the re mainder of the cycle; and means for yieldably stopping said other member prior to the holding thereof.

In an engine, a cylinder having -a head; a piston comprising an open ended sleeve member, slidable within said cylinder and a core member slidable within said sleeve, said core being connected with the engine crank shaft, and said sleeve moving therewith during a portion of the cycle; means controlled by said core for holding said sleeve stationary during the remainder of the cycle;

and means for yieldably limiting the movement of said sleeve when approaching said cylinder head.

In an engine, a cylinder; a piston comprising a sleeve member slidable within said cylinder and a core member slidable within said sleeve, one of said members being connected with the engine crank shaft; means for holding the other member stationary; means controlled by the shaft-connected member for periodically releasing said holding means; and means controllable at will for rendering said releasing means inopera- I tive.

In testimony whereof I have signed my name to this specification.

- DAVID PRI-NGLE SAVAGE. 

